In recent years proteins and enzymes have been immobilized on a variety of support materials, and such immobilization has commonly been achieved by covalent attachment, entrapment in hydrophilic gels, or by adsorption. Immobilized enzymes have attracted considerable attention because of their advantages of economy (expensive enzymes can be readily recovered and reused), convenience (immobilized enzymes can be removed readily without contaminating the solution being treated), and stability (most enzymes are more stable when immobilized). The advantages and uses of immobilized enzymes have been summarized in several reviews: Silman and Katchalski, Ann. Rev. Biochem. 35, 873 (1966); Vieth and Venkatasubramanian, Chem. Tech. 677 (1973), 47 (1974); Zaborsky, New Scientist, 719 (1973); Goldstein, Methods Enzymol. XIX, 935 (1970), Mosbach Sci. Amer. 224(3), 26 (1971).
Methods for immobilization of proteins by either covalent attachment or by entrapment in gels usually require somewhat exotic chemistry, and/or expensive and sometimes toxic reagents. Moreover, usually only a small portion of the protein supplied actually becomes immobilized and biologically active. In contrast, immobilization by adsorption is much more convenient and inexpensive because no covalent chemical bond is formed between the protein and the support. However, adsorption is generally not strong enough to completely immobilize the protein; with some supports, for example, subsequent tanning with formaldehyde is necessary to provide sufficient strong binding [Weston and Avrameas, Biochem. Biophys. Res. Commun. 45, 1574 (1974); Olson and Stanley, Agr. Food Chem. 21, 440 (1973)]. Alternatively, stronger adsorption can be sometimes obtained with specific affinity reagents, however, preparation of these supports again involves rather complex chemistry.
Since most proteins are felt to be associated to some degree with hydrophobic membranes in the cell where they naturally function, they might be expected to similarly associate with artificially supplied hydrophobic materials. Indeed, a few recent reports of hydrophobic chromatography have indicated that proteins can associate with such hydrophobic materials [Er-el, Zaidenzaig and Shaltiel, Biochem. Biophys. Res. Comm. 49, 383 (1972); Hofstee, Anal. Biochem. 52, 430 (1973); Shaltiel and Er-el, Proc. Natl. Acad. Sci. U.S. 70, 778 (1973); and Yon, Biochem. J. 137, 127 (1974)].
Heretofore, however, a hydrophobic support has not been prepared and utilized that achieves substantially complete immobilization by adsorption with no covalent chemical bond being formed between the protein and the support.